#include <types.h>
#include <x86.h>
#include <error.h>
#include <stdio.h>
#include <string.h>

/* *
 * Space or zero padding and a field width are supported for the numeric
 * formats only.
 *
 * The special format %e takes an integer error code
 * and prints a string describing the error.
 * The integer may be positive or negative,
 * so that -E_NO_MEM and E_NO_MEM are equivalent.
 * */

static const char * const error_string[MAXERROR + 1] = {
	[0]						NULL,
	[E_UNSPECIFIED]			"unspecified error",
	[E_BAD_PROC]			"bad process",
	[E_INVAL]				"invalid parameter",
	[E_NO_MEM]				"out of memory",
	[E_NO_FREE_PROC]		"out of processes",
	[E_FAULT]				"segmentation fault",
};

/* *
 * printnum - print a number (base <= 16) in reverse order
 * @putch:		specified putch function, print a single character
 * @putdat:		used by @putch function
 * @num:		the number will be printed
 * @base:		base for print, must be in [1, 16]
 * @width: 		maximum number of digits, if the actual width is less than @width, use @padc instead
 * @padc:		character that padded on the left if the actual width is less than @width
 * */
static void
printnum(void (*putch)(int, void*), void *putdat,
		unsigned long long num, unsigned base, int width, int padc) {
	unsigned long long result = num;
	unsigned mod = do_div(result, base);

	// first recursively print all preceding (more significant) digits
	if (num >= base) {
		printnum(putch, putdat, result, base, width - 1, padc);
	} else {
		// print any needed pad characters before first digit
		while (-- width > 0)
			putch(padc, putdat);
	}
	// then print this (the least significant) digit
	putch("0123456789abcdef"[mod], putdat);
}

/* *
 * getuint - get an unsigned int of various possible sizes from a varargs list
 * @ap:			a varargs list pointer
 * @lflag:		determines the size of the vararg that @ap points to
 * */
static unsigned long long
getuint(va_list *ap, int lflag) {
	if (lflag >= 2) {
		return va_arg(*ap, unsigned long long);
	}
	else if (lflag) {
		return va_arg(*ap, unsigned long);
	}
	else {
		return va_arg(*ap, unsigned int);
	}
}

/* *
 * getint - same as getuint but signed, we can't use getuint because of sign extension
 * @ap:			a varargs list pointer
 * @lflag:		determines the size of the vararg that @ap points to
 * */
static long long
getint(va_list *ap, int lflag) {
	if (lflag >= 2) {
		return va_arg(*ap, long long);
	}
	else if (lflag) {
		return va_arg(*ap, long);
	}
	else {
		return va_arg(*ap, int);
	}
}

/* *
 * printfmt - format a string and print it by using putch
 * @putch:		specified putch function, print a single character
 * @putdat:		used by @putch function
 * @fmt:		the format string to use
 * */
void
printfmt(void (*putch)(int, void*), void *putdat, const char *fmt, ...) {
	va_list ap;

	va_start(ap, fmt);
	vprintfmt(putch, putdat, fmt, ap);
	va_end(ap);
}

/* *
 * vprintfmt - format a string and print it by using putch, it's called with a va_list
 * instead of a variable number of arguments
 * @putch:		specified putch function, print a single character
 * @putdat:		used by @putch function
 * @fmt:		the format string to use
 * @ap:			arguments for the format string
 *
 * Call this function if you are already dealing with a va_list.
 * Or you probably want printfmt() instead.
 * */
void
vprintfmt(void (*putch)(int, void*), void *putdat, const char *fmt, va_list ap) {
	register const char *p;
	register int ch, err;
	unsigned long long num;
	int base, width, precision, lflag, altflag;

	while (1) {
		while ((ch = *(unsigned char *)fmt ++) != '%') {
			if (ch == '\0') {
				return;
			}
			putch(ch, putdat);
		}

		// Process a %-escape sequence
		char padc = ' ';
		width = precision = -1;
		lflag = altflag = 0;

	reswitch:
		switch (ch = *(unsigned char *)fmt ++) {

		// flag to pad on the right
		case '-':
			padc = '-';
			goto reswitch;

		// flag to pad with 0's instead of spaces
		case '0':
			padc = '0';
			goto reswitch;

		// width field
		case '1' ... '9':
			for (precision = 0; ; ++ fmt) {
				precision = precision * 10 + ch - '0';
				ch = *fmt;
				if (ch < '0' || ch > '9') {
					break;
				}
			}
			goto process_precision;

		case '*':
			precision = va_arg(ap, int);
			goto process_precision;

		case '.':
			if (width < 0)
				width = 0;
			goto reswitch;

		case '#':
			altflag = 1;
			goto reswitch;

		process_precision:
			if (width < 0)
				width = precision, precision = -1;
			goto reswitch;

		// long flag (doubled for long long)
		case 'l':
			lflag ++;
			goto reswitch;

		// character
		case 'c':
			putch(va_arg(ap, int), putdat);
			break;

		// error message
		case 'e':
			err = va_arg(ap, int);
			if (err < 0) {
				err = -err;
			}
			if (err > MAXERROR || (p = error_string[err]) == NULL) {
				printfmt(putch, putdat, "error %d", err);
			}
			else {
				printfmt(putch, putdat, "%s", p);
			}
			break;

		// string
		case 's':
			if ((p = va_arg(ap, char *)) == NULL) {
				p = "(null)";
			}
			if (width > 0 && padc != '-') {
				for (width -= strnlen(p, precision); width > 0; width --) {
					putch(padc, putdat);
				}
			}
			for (; (ch = *p ++) != '\0' && (precision < 0 || -- precision >= 0); width --) {
				if (altflag && (ch < ' ' || ch > '~')) {
					putch('?', putdat);
				}
				else {
					putch(ch, putdat);
				}
			}
			for (; width > 0; width --) {
				putch(' ', putdat);
			}
			break;

		// (signed) decimal
		case 'd':
			num = getint(&ap, lflag);
			if ((long long)num < 0) {
				putch('-', putdat);
				num = -(long long)num;
			}
			base = 10;
			goto number;

		// unsigned decimal
		case 'u':
			num = getuint(&ap, lflag);
			base = 10;
			goto number;

		// (unsigned) octal
		case 'o':
			num = getuint(&ap, lflag);
			base = 8;
			goto number;

		// pointer
		case 'p':
			putch('0', putdat);
			putch('x', putdat);
			num = (unsigned long long)(uintptr_t)va_arg(ap, void *);
			base = 16;
			goto number;

		// (unsigned) hexadecimal
		case 'x':
			num = getuint(&ap, lflag);
			base = 16;
		number:
			printnum(putch, putdat, num, base, width, padc);
			break;

		// escaped '%' character
		case '%':
			putch(ch, putdat);
			break;

		// unrecognized escape sequence - just print it literally
		default:
			putch('%', putdat);
			for (fmt --; fmt[-1] != '%'; fmt --)
				/* do nothing */;
			break;
		}
	}
}

/* sprintbuf is used to save enough information of a buffer */
struct sprintbuf {
	char *buf;			// address pointer points to the first unused memory
	char *ebuf;			// points the end of the buffer
	int cnt;			// the number of characters that have been placed in this buffer
};

/* *
 * sprintputch - 'print' a single character in a buffer
 * @ch:			the character will be printed
 * @b:			the buffer to place the character @ch
 * */
static void
sprintputch(int ch, struct sprintbuf *b) {
	b->cnt ++;
	if (b->buf < b->ebuf) {
		*b->buf ++ = ch;
	}
}

/* *
 * snprintf - format a string and place it in a buffer
 * @str:		the buffer to place the result into
 * @size:		the size of buffer, including the trailing null space
 * @fmt:		the format string to use
 * */
int
snprintf(char *str, size_t size, const char *fmt, ...) {
	va_list ap;
	int cnt;
	va_start(ap, fmt);
	cnt = vsnprintf(str, size, fmt, ap);
	va_end(ap);
	return cnt;
}

/* *
 * vsnprintf - format a string and place it in a buffer, it's called with a va_list
 * instead of a variable number of arguments
 * @str:		the buffer to place the result into
 * @size:		the size of buffer, including the trailing null space
 * @fmt:		the format string to use
 * @ap:			arguments for the format string
 *
 * The return value is the number of characters which would be generated for the
 * given input, excluding the trailing '\0'.
 *
 * Call this function if you are already dealing with a va_list.
 * Or you probably want snprintf() instead.
 * */
int
vsnprintf(char *str, size_t size, const char *fmt, va_list ap) {
	struct sprintbuf b = {str, str + size - 1, 0};
	if (str == NULL || b.buf > b.ebuf) {
		return -E_INVAL;
	}
	// print the string to the buffer
	vprintfmt((void*)sprintputch, &b, fmt, ap);
	// null terminate the buffer
	*b.buf = '\0';
	return b.cnt;
}

